1. Field of the Invention
The present invention relates to toner used for copying machines and printers practically applying electrophotographic technology, and a method for production thereof, a toner kit, as well as a developer, a process cartridge, an image forming method and an image forming apparatus.
2. Description of the Related Art
Conventionally, in electrophotography, a latent electrostatic image formed by charging and exposing a surface of a photoconductor (hereinafter sometimes also referred to as an “image bearing member”, a “latent electrostatic image bearing member” or an “electrophotographic photoconductor”) is developed with toner to form a toner image, the toner image is transferred onto a recording media such as transfer paper, and this is fixed by a heating roll to form an image.
In a dry developing method employed in electrophotographs and electrostatic recording, there are a method of using a two-component developer composed of the toner and a carrier and a method of using one-component developer containing no carrier. In the method of using the two-component developer, good images are obtained relatively stably, but there is a shortcoming in that an apparatus constitution becomes large. Meanwhile, in the method of using the one-component developer, typically the toner (developer) is fed by at least one toner feeding member, and an electrostatic image formed on an image bearing member by the toner is made into a visible image. At that time, a thickness of a toner layer fed on the surface of the toner feeding member must be thinned as possible. In particular, since this toner is necessary to be charged by a development apparatus when the toner having high electric resistance is used, the thickness of the toner layer must be formed extremely thinly. This is because if the toner layer is thick, only a vicinity of the surface of the toner layer is charged and the entire toner layer is hardly charged uniformly.
From such a request, as a unit (toner layer thickness regulating unit) which regulates the thickness of the toner layer on the toner feeding member, various methods are proposed. As a representative example, a regulatory blade is used, the regulatory blade is opposed to the toner feeding member, and the toner fed on the toner feeding member is pushed down with the regulatory blade to control the thickness of the toner layer. A type in which a roller in place of the regulatory blade is abutted to the surface of the toner feeding member to obtain the same effect has been also proposed.
In a developing, in the toner layer formed on the surface of a developing sleeve by a developer layer thickness regulating member, the toner present in the vicinity of the surface of the developing sleeve has extremely high charge, is attracted by a mirroring force to the surface of the developing sleeve and becomes an immobilized state on the surface of the developing sleeve. Thus, the toner does not migrate from the developing sleeve to a latent image on an image bearing member, and a charge-up phenomenon easily occurs. In particular, the charge-up phenomenon easily occurs under low humidity.
When such a charge-up phenomenon occurs, the toner in an upper layer of the toner layer formed on the developing sleeve is hardly charged, and thus, an amount of the charged toner is reduced. As a result, scumming in non-image sections, toner leaking and toner scattering easily occur.
To eliminate such phenomena, it is necessary to control the amount of the charged toner in the toner layer formed on the developing sleeve as uniformly as possible.
When a developing roller is a metal and the regulatory blade is a resin, if the toner having a different charge property is used, developing members, particularly the regulatory blade and a development setup must be individually changed, leading to being complicated and simultaneously cost up.
Meanwhile, when the developing roller is the resin and the regulatory blade is the metal, the developing members, particularly a developing roller member and the development setup must be individually changed, leading to being complicated and simultaneously cost up.
Here, for the black toner, since carbon black usually used is conductive, a charge keeping capacity of the black toner itself is lower than that of the color toner. For example, in the black toner described in Japanese Patent Application Laid-Open (JP-A) No. 10-246987, a benzyl boron-based charge controlling agent is used, and since originally the charge-up is hardly made, defect of charge hardly occurs.
In JP-A No. 5-165257, the benzyl boron-based charge controlling agent is used for the color toner. Since an existing state of the charge controlling agent is not controlled, if the charge controlling agent is abundantly present in the vicinity of the surface, an internal resistance is kept high and the charge-up is not inhibited. If the amount of charge controlling agent in the vicinity of the surface is small, the surface resistance becomes also high, and the charge-up occurs or the charge is reduced because the charge controlling agent is not functioned.
A salicylic acid-based charge controlling agents described in JP-A No. 10-246987 are colorless or almost colorless, and thus, are preferably used for the color toner. But, since these have the effect to generate the charge but do not leak the charge, the charge-up phenomenon easily occurs. When the charge-up phenomenon of the toner occurs, a distribution of the charged toner on the developing roller becomes broad, and the scumming and density reduction are caused.
In JP-A No. 2004-117551, benzyl boron-based charge controlling agents are used in the black toner and the color toner. However, in this proposal, since the existing state of the charge controlling agent is not controlled, difference occurs in charge property between the black toner and the color toner. Under a high temperature and high humidity environment and a low temperature and low humidity environment, density transition is different. Thus, development control for full color images becomes complicated.